Based upon a comprehensive study of 123 copper deposits in China. this paper reaches the following conclusions: 1. The crust in China was solidified pretty late; with the accretion of the plate, the copper mineralizat...Based upon a comprehensive study of 123 copper deposits in China. this paper reaches the following conclusions: 1. The crust in China was solidified pretty late; with the accretion of the plate, the copper mineralization moved towards its margin in space and became successively younger in age. 2. The major copper ore types ever found in the world have mostly been discovered in China, in which the porphyry type seems to be the most important and the massive sulfide type in the transitional bed between marine clastic and carbonate rocks is clearly defined. 3. Carbonate strata are widespread in China and their deposition lasted for a long geological period, so the proportion of copper deposits occurring in them is large as compared with other parts of the world. 4. Seven metallogenic epochs can be recognized, in which the Mesozoic one plays the leading role and the middle(late) Palaeozoic and Cenozoic ones are next in importance. Mineralization was comparatively simple in the early geological period. and became diversified later on. In the early epochs copper deposits related to basaltic magmatism and metamorphosed marine sediments predominated, whereas in the later epochs those related to granitic magmatism and continental sedimentation were dominant. 5. There exist in China thirteen metallogenic provinces, of which the Lower Yangtze downwarping belt, Sanjiang fold system, Jiangnan axis and Xikang-Yunnan axis are of greater significance. 6. The crustal mobility in China was rather pronounced, the polycyclic evolution of the crust has resulted in such obvious phenomena as the inheritance of mineralization, the coexistence of various types and the superposition of different genetic types.展开更多
Marine biodiversity is changing in response to altered physical environment, subsequent ecological changes as well as anthropogenic disturbances. In this study, phytoplankton samples in situ collected in the Bering Se...Marine biodiversity is changing in response to altered physical environment, subsequent ecological changes as well as anthropogenic disturbances. In this study, phytoplankton samples in situ collected in the Bering Sea in July of 1999 and 2010 were analyzed to obtain phytoplankton community structure and spatial-temporal variation between the beginning and end of this decade, and the correlation of phytoplankton community dynamics and environmental factors was investigated. A total of 5 divisions, 58 genera and 153 species of phytoplankton belonging to 3 ecological groups were identified. The vast majority of phytoplankton consisted of diatoms accounting for 66.7% of the total species and 95.2% of the total abundance. Considering differentiation in spatial extent and phytoplankton sample types, there were subtle changes in species composition, large altering in abundance and significant variation in spatial distribution between two surveys. The abundance peak area was located at the Bering Strait while sub peak was found at the Bering Sea Basin. The boreal-temperate diatom was the dominant flora, which was subsequently replaced by eurythermal and frigid-water diatom. Phytoplankton community in the Bering Sea was not a simplex uniform community but composed of deep-ocean assemblage and neritic assemblage. The deep-ocean assemblage was located in the northwestern Pacific Ocean and Bering Sea Basin, dominated by boreal-temperate species（Neodenticula seminae, Thalassiothrix longissima, Amphiprora hyperborean, Chaetoceros atlanticus, Thalassiosira trifulta, etc.） and eurychoric species（Thalassionema nitzschioides, Ch. compressus, Rhizosolenia styliformis, etc.）, and characterized by low abundance, even interspecies abundance allocations, diverse dominant species and high species diversity. The neritic assemblage was distributed on the continental shelf and slope of Bering Sea and was mainly composed of frigid-water species（Th.nordenski？ldii, Ch. furcellatus, Ch. socialis, Bacteriosira fragilis, etc.） and eurythermal and euryhaline species（L.danicus, Ch. curvisetus, Coscinodiscus curvatulus, etc.）, and it was characterized by high abundance, uneven interspecies allocations, prominent dominant species and low species diversity. Spatial-temporal variation of species composition and abundance of phytoplankton in the Bering Sea was directly controlled by surface circulation,nutrient supply and ice edge.展开更多
With the rapid development of rail transit,effectively developing urban underground space(UUS)in the metro zone has become an important approach to expanding urban space.However,UUS is currently facing problems,such a...With the rapid development of rail transit,effectively developing urban underground space(UUS)in the metro zone has become an important approach to expanding urban space.However,UUS is currently facing problems,such as an uneven distribution or even loss of vitality,which restricts the utilization efficiency of the space.Thus,we established a UUS environmental assessment system based on the‘‘comfort-aesthetic-function-traffic-structure”using space syntax,instrumental measurement,and questionnaire surveys.By constructing a partial-least-square structural equation model,the internal relationships between the UUS environment and corresponding space vitality and space perception under different study areas,namely the underground transportation-oriented space(transportation space for short)and the underground commercial-oriented space(commercial space for short),were studied in detail throughout the working day.Results indicate the following:(1)the UUS in the metro zone environment influences spatial vitality.The vitality distribution of transportation space is significantly affected by the spatial traffic and structure.The vitality distribution of commercial space is significantly affected by the spatial function and traffic.(2)The environment of UUSs in the metro zone influences users’s perception.The perception of transportation space is significantly affected by aesthetics and comfort.The perception of commercial space is significantly affected by aesthetic,comfort,and spatial functions.(3)The user’s perception affects vitality,and the effect is more significant in commercial space.This study provides an in-depth understanding of the relationship between the complex environment and its spatial vitality as well as the spatial perception of the UUS in metro zones.Our research results provide a novel approach and theoretical basis for the development and application of UUS vitality in various cities.展开更多
In this paper,a reaction-diffusion SEI epidemic model with nonlinear incidence rate is proposed.The well-posedness of solutions is studied,including the existence of positive and unique classical solution and the exis...In this paper,a reaction-diffusion SEI epidemic model with nonlinear incidence rate is proposed.The well-posedness of solutions is studied,including the existence of positive and unique classical solution and the existence and the ultimate boundedness of global solutions.The basic reproduction numbers are given in both heterogeneous and homogeneous environments.For spatially heterogeneous environment,by the comparison principle of the diffusion system,the infection-free steady state is proved to be globally asymptotically stable if R_(0)<1,if R_(0)>1,the system will be persistent and admit at least one positive steady state.For spatially homogenous environment,by constructing a Lyapunov function,the infect ion-free steady state is proved to be globally asymptotically stable if,R_(0)<1,and then the unique positive steady state is achieved and is proved to be globally asymptotically stable if R_(0)>1.Finally,two examples are given via numerical simulations,and then some control strategies are also presented by the sensitive analysis.展开更多
High-temperature warnings frequently occurred at the Power Distribution System(PDS)of the Alpha Magnetic Spectrometer(AMS).To investigate the fundamental reasons,a theoretical model for the AMS PDS was established und...High-temperature warnings frequently occurred at the Power Distribution System(PDS)of the Alpha Magnetic Spectrometer(AMS).To investigate the fundamental reasons,a theoretical model for the AMS PDS was established under the International Space Station(ISS)normal and special operating conditions.With the model,the study investigated the external heat fluxes and the temperature responses of the PDS.The effects of ISS special operations on the PDS’s thermal environment were also investigated.Results reveal that the total external heat flux at the PDS reaches its maximum value when the angleβis around–25°,where high-temperature warning frequently occurs.Under the ISS normal operating condition,the temperature response hysteresis at the PDS varies from 116 s to 230 s.When the ISS performed special operations,locking the ISS solar arrays had the greatest influence on the PDS’s external heat fluxes,and the average temperature at the PDS fell by 1.7°C.When the ISS performed multiple special operations,simultaneously locking the ISS solar arrays and adjusting the ISS flight attitude were the most frequent operations,of which the influences on the PDS temperature were the largest,i.e.,the changes in peak temperature reached up to+2.5°C.展开更多
文摘Based upon a comprehensive study of 123 copper deposits in China. this paper reaches the following conclusions: 1. The crust in China was solidified pretty late; with the accretion of the plate, the copper mineralization moved towards its margin in space and became successively younger in age. 2. The major copper ore types ever found in the world have mostly been discovered in China, in which the porphyry type seems to be the most important and the massive sulfide type in the transitional bed between marine clastic and carbonate rocks is clearly defined. 3. Carbonate strata are widespread in China and their deposition lasted for a long geological period, so the proportion of copper deposits occurring in them is large as compared with other parts of the world. 4. Seven metallogenic epochs can be recognized, in which the Mesozoic one plays the leading role and the middle(late) Palaeozoic and Cenozoic ones are next in importance. Mineralization was comparatively simple in the early geological period. and became diversified later on. In the early epochs copper deposits related to basaltic magmatism and metamorphosed marine sediments predominated, whereas in the later epochs those related to granitic magmatism and continental sedimentation were dominant. 5. There exist in China thirteen metallogenic provinces, of which the Lower Yangtze downwarping belt, Sanjiang fold system, Jiangnan axis and Xikang-Yunnan axis are of greater significance. 6. The crustal mobility in China was rather pronounced, the polycyclic evolution of the crust has resulted in such obvious phenomena as the inheritance of mineralization, the coexistence of various types and the superposition of different genetic types.
基金The National Natural Science Foundation of China under contract Nos 41306116 and 41506217the Basic Research of the National Department of Science and Technology under contract No.GASI-01-02-04the Polar Science Strategic Research Foundation of China under contract No.20140309
文摘Marine biodiversity is changing in response to altered physical environment, subsequent ecological changes as well as anthropogenic disturbances. In this study, phytoplankton samples in situ collected in the Bering Sea in July of 1999 and 2010 were analyzed to obtain phytoplankton community structure and spatial-temporal variation between the beginning and end of this decade, and the correlation of phytoplankton community dynamics and environmental factors was investigated. A total of 5 divisions, 58 genera and 153 species of phytoplankton belonging to 3 ecological groups were identified. The vast majority of phytoplankton consisted of diatoms accounting for 66.7% of the total species and 95.2% of the total abundance. Considering differentiation in spatial extent and phytoplankton sample types, there were subtle changes in species composition, large altering in abundance and significant variation in spatial distribution between two surveys. The abundance peak area was located at the Bering Strait while sub peak was found at the Bering Sea Basin. The boreal-temperate diatom was the dominant flora, which was subsequently replaced by eurythermal and frigid-water diatom. Phytoplankton community in the Bering Sea was not a simplex uniform community but composed of deep-ocean assemblage and neritic assemblage. The deep-ocean assemblage was located in the northwestern Pacific Ocean and Bering Sea Basin, dominated by boreal-temperate species（Neodenticula seminae, Thalassiothrix longissima, Amphiprora hyperborean, Chaetoceros atlanticus, Thalassiosira trifulta, etc.） and eurychoric species（Thalassionema nitzschioides, Ch. compressus, Rhizosolenia styliformis, etc.）, and characterized by low abundance, even interspecies abundance allocations, diverse dominant species and high species diversity. The neritic assemblage was distributed on the continental shelf and slope of Bering Sea and was mainly composed of frigid-water species（Th.nordenski？ldii, Ch. furcellatus, Ch. socialis, Bacteriosira fragilis, etc.） and eurythermal and euryhaline species（L.danicus, Ch. curvisetus, Coscinodiscus curvatulus, etc.）, and it was characterized by high abundance, uneven interspecies allocations, prominent dominant species and low species diversity. Spatial-temporal variation of species composition and abundance of phytoplankton in the Bering Sea was directly controlled by surface circulation,nutrient supply and ice edge.
基金supported by the Natural Science Research Project of Anhui Educational Committee,China(Grant No.2022AH050845)Major project of the National Natural Science Foundation of China(Grant No.52090080)+6 种基金Special project of Chinese Academy of Engineering and National Natural Science Foundation of China(Grant No.L1924061)Teaching Research Project in Anhui Province,China(Grant No.2020jyxm1819)Scientific Research Foundation for High-level Talents of Anhui University of Science and Technology,China(Grant No.2022yjrc83)Humanity and Social Science Research Project of Anhui Educational Committee,China(Grant No.SK2021A0211)Anhui Province Science and Technology Plan Project of Housing Urban-rural Construction,China(Grant Nos.2020-YF12 and 2020-YF14)Major Science and Technology Projects of Guangdong Province,China(Grant No.192019071811500001)the Research Project of Huainan Science and Technology Bureau,China(Grant No.2020141).
文摘With the rapid development of rail transit,effectively developing urban underground space(UUS)in the metro zone has become an important approach to expanding urban space.However,UUS is currently facing problems,such as an uneven distribution or even loss of vitality,which restricts the utilization efficiency of the space.Thus,we established a UUS environmental assessment system based on the‘‘comfort-aesthetic-function-traffic-structure”using space syntax,instrumental measurement,and questionnaire surveys.By constructing a partial-least-square structural equation model,the internal relationships between the UUS environment and corresponding space vitality and space perception under different study areas,namely the underground transportation-oriented space(transportation space for short)and the underground commercial-oriented space(commercial space for short),were studied in detail throughout the working day.Results indicate the following:(1)the UUS in the metro zone environment influences spatial vitality.The vitality distribution of transportation space is significantly affected by the spatial traffic and structure.The vitality distribution of commercial space is significantly affected by the spatial function and traffic.(2)The environment of UUSs in the metro zone influences users’s perception.The perception of transportation space is significantly affected by aesthetics and comfort.The perception of commercial space is significantly affected by aesthetic,comfort,and spatial functions.(3)The user’s perception affects vitality,and the effect is more significant in commercial space.This study provides an in-depth understanding of the relationship between the complex environment and its spatial vitality as well as the spatial perception of the UUS in metro zones.Our research results provide a novel approach and theoretical basis for the development and application of UUS vitality in various cities.
基金supported by the National Natural Science Foundation of China(Grant No.11871475)the Hunan Provincial Innovation Foundation for Postgraduate(Grant No.CX20200096)the Fundamental Research Funds for the Central Universities of Central South University(Grant No.2020zzts024).
文摘In this paper,a reaction-diffusion SEI epidemic model with nonlinear incidence rate is proposed.The well-posedness of solutions is studied,including the existence of positive and unique classical solution and the existence and the ultimate boundedness of global solutions.The basic reproduction numbers are given in both heterogeneous and homogeneous environments.For spatially heterogeneous environment,by the comparison principle of the diffusion system,the infection-free steady state is proved to be globally asymptotically stable if R_(0)<1,if R_(0)>1,the system will be persistent and admit at least one positive steady state.For spatially homogenous environment,by constructing a Lyapunov function,the infect ion-free steady state is proved to be globally asymptotically stable if,R_(0)<1,and then the unique positive steady state is achieved and is proved to be globally asymptotically stable if R_(0)>1.Finally,two examples are given via numerical simulations,and then some control strategies are also presented by the sensitive analysis.
基金support from Shandong Universitysponsored by the Fundamental Research Fund of Shandong University,China。
文摘High-temperature warnings frequently occurred at the Power Distribution System(PDS)of the Alpha Magnetic Spectrometer(AMS).To investigate the fundamental reasons,a theoretical model for the AMS PDS was established under the International Space Station(ISS)normal and special operating conditions.With the model,the study investigated the external heat fluxes and the temperature responses of the PDS.The effects of ISS special operations on the PDS’s thermal environment were also investigated.Results reveal that the total external heat flux at the PDS reaches its maximum value when the angleβis around–25°,where high-temperature warning frequently occurs.Under the ISS normal operating condition,the temperature response hysteresis at the PDS varies from 116 s to 230 s.When the ISS performed special operations,locking the ISS solar arrays had the greatest influence on the PDS’s external heat fluxes,and the average temperature at the PDS fell by 1.7°C.When the ISS performed multiple special operations,simultaneously locking the ISS solar arrays and adjusting the ISS flight attitude were the most frequent operations,of which the influences on the PDS temperature were the largest,i.e.,the changes in peak temperature reached up to+2.5°C.
